Fix mpls_label match view in ofl-strcurs-print.c

Fix mpls_label match view in ofl-strcurs-print.c 
Should cast the value before getting the int32 out of it 

case OFPXMT_OFB_MPLS_LABEL:
			fprintf(stream, "mpls_label=\"0x%lx\"",( *(uint32_t*)f->value) & 0x000fffff);

instead of

fprintf(stream, "mpls_label=\"%d\"",((uint32_t) *f->value) & 0x000fffff);